Field of the Invention
The invention relates to a method for testing an internal combustion engine. The engine is driven under traction by an electric motor, and the internal combustion engine is brought to a predetermined rotational speed.
A method of this type is known from Published, Non-Prosecuted German Patent Application DE 196 54 137 A1, European Patent EP 0 456 244 B1 and Published, European Patent Application EP 0 536 561 A1. Testing is carried out here by the torque of the electric traction motor being measured, specific torque values being an indication of faulty engines.
Furthermore, U.S. Pat. No. 4,448,063 discloses a method for testing an internal combustion engine, in which oil under pressure is introduced as a test medium.
Determining the torque values is a complicated method and may lead to inaccurate measurement results.
It is accordingly an object of the invention to provide a method for testing an internal combustion enginge for assembly and/or manufacturing faults that overcomes the above-mentioned disadvantages of the prior art methods of this general type, which does not require any torque measurement values.
With the foregoing and other objects in view there is provided, in accordance with the invention, a method for testing internal combustion engines for assembly and manufacturing faults. The method includes the steps of driving an internal combustion engine under traction with an electric motor; bringing the internal combustion engine to a predetermined rotational speed; measuring a volume of air entering a crankcase ventilation system of the internal combustion engine during a traction movement; comparing a measured air volume with desired values of a fault-free internal combustion engine; and inferring at least one of an assembly fault and a manufacturing fault being present if the measured air volume deviates from the desired values.
Accordingly, during, the traction movement, the air volume entering the crankcase ventilation is measured the measurement value is compared with desired values of a fault-free internal combustion engine and assembly and/or manufacturing faults are inferred from deviations. The air volume passing the piston rings and/or the valve-stem gasket is determined, along the path that it follows through the crankcase via the crankcase ventilation, by a suitable measuring device.
Accurate fault detection is achieved by this path which is independent of the torque of the electric motor.
Preferably, during the traction movement, an outlet duct of the internal combustion engine is at least temporarily closed.
As a result of this measure, during the exhaust stroke, the pressure in the combustion space of the internal combustion engine rises, which represents a rise in the volume flow entering the crankcase ventilation.
In order to achieve an automatic test sequence, characteristic faults, such as, for example, the absence of a specific piston ring or of a valve-stem gasket, are simulated, so that direct reference values are available.
Particularly in order to detect the absence of a valve-stem gasket, a supporting pressure is applied on the suction side or delivery side, the increased volume quantity being maintained by the slide in the intake or outlet pipe being closed.
In accordance with another mode of the invention, there is the step of setting the predetermined rotational speed to be between 15 minxe2x88x921 and 100 minxe2x88x921.
In accordance with a concomitant mode of the invention, there is the step of applying a supporting pressure on an exhaust-gas side of the internal combustion engine.
Other features which are considered as characteristic for the invention are set forth in the appended claims.
Although the invention is illustrated and described herein as embodied in a method for testing an internal combustion enginge for assembly and/or manufacturing faults, it is nevertheless not intended to be limited to the details shown, since various modifications and structural changes may be made therein without departing from the spirit of the invention and within the scope and range of equivalents of the claims.
The construction and method of operation of the invention, however, together with additional objects and advantages thereof will be best understood from the following description of specific embodiments when read in connection with the accompanying drawings.